Same thing here, but t's my right front turn signal...

When I got the car (used, 30k miles), one of the interior lamps didn't work. I opened it up to check the bulb and found out that it was just a bad contact - must be a common issue. I simply cleaned (scraped) the interor socket and bulb contacs with my pocket knife, and it's still going strong.

I'm gonna try some DeOxIt on the turn signal socket...